Engine trouble: This brown bear looks ready to set sail at Brooks River in Katmai National Park, Alaska

As if the fish didn't have it hard enough already...This brown bear looked ready to give chase as it clambered into a boat on Brooks River, Alaska.The rib-tickling shot forms part of a series captured in national parks across the remote U.S. territory, where photographer Doug Howie travelled to document wild bears in their natural habitat.The rest of the shoot yielded some fascinating glimpses of bear behaviour.Two of the fierce beasts were caught locked in paw-to-paw combat in Katmai National Park - also home to the four-legged sailor.

Round one: Two fearsome Alaskan brown bears trade bites and blows as they spar in Katmai National Park, Alask

In Glacier Bay National Park and Reserve, meanwhile, a mother is seen leading her cubs across plains and rivers.And in Kodiak National Wildlife Refuge, heartwarming scenes found another mother bear roughhousing playfully with her pack of year-old cubs.

Low blow: The brown bears swipe their enormous paws at each other after a scrap breaks out by the river at Katmai National Park

Keeping pace: Two cubs follow their mother across the river at Glacier Bay National Park and Preserve in Alaska

Rough and tumble: A mother plays with her two yearling cubs at Kodiak National Wildlife Refuge in Kodiak, Alaska

Patience: The mother bear puts up with her cub's mischief as it tries to gnaw on her chin

That's enough! One of the cubs looks as if it is trying to calm its over-excited sibling as it plays rough with their mother